高中历史研究性学习的特点是什么
参考答案：(1)开放性；(2)过程性；(3)主体性；(4)综合性。
根据句意和汉语注释，写出单词的正确形式。
小题1:As we know, oil always __________ (漂浮) on water.
小题2:He __________ (点头) to me in greeting when I entered the room.
小题3:We are very __________ (自豪) that a pupil from our school has won the prize.
小题4:They all hurried __________ (往楼上) to see what was going on.
小题5:There was __________ (沉默) for a moment and then someone made a useful suggestion.
对第四脑室的叙述正确的是()
A．上通中脑水管，下通脊髓中央管
B．此处脉络丛不产生脑脊液
C．有不成对的外侧孔
D．顶是菱形窝，底朝向小脑
E．有成对的正中孔
